What can you do to recalibrate the speedometer after a tire change?

I put on 265/75 16's and I'm off about 7%.

 

What year?

 

97's and some (I think) 98's you can get a different gear for your VSS vehicle speed sensor. 98's and up you have to do it on your truck's computer. I have a 97 and it took me maybe 5 minutes to change the VSS gear.

 

Sorry, it's a 99 F-150 4wd

 

There are "power programmers" sold by superchips et al that will program your truck for different tire sizes, or your dealer should be able to do it for you. As I understand it they can just plug into your service port and change the size.